The ACT Fire Brigade has confirmed the fire is burning within an amount of mineral oil within the building.
Firefighters are now re-commencing firefighting operations using water and foam.
The ACT Fire Brigade has now ordered the evacuation of the whole suburb of Mitchell including a number of campers at Exhibition Park.
There is still a localised smoke plume but there is no threat to nearby residential suburbs of Harrison and Franklin.
Residents are advised to remain indoors.